The Student Room Group

Fluids, Bernoulli equation on split flow

Attached the question (I've looked at the answers btw so I'm asking why not how). Heres what I don't understand.

A) z1=z2 ? There's a definite decrease in potential energy as the lower tube is of 30 degrees to the horizontal where as the upper is only 15

B) they used the Bernoulli equation between section 1 (I.e the inlet big tube) and the (upper outlet 100mm one). You can't do that!! How can you forget about the second outlet?? They didn't add in the second outlet velocity??

I guess what I'm trying to say is, if Bernoulli equation is dependent on energy conservation how can you forget about the lower tube when working out the pressure at section 1?

Any ideas ? I'll explain my q a bit better if you don't get it
image.jpg513.0KB
image.jpg512.8KB
There are some qs on the paper which are the same im asking on here
Damn it someone help
Right I forgot to read the question Lul. I understand A of my question, It says they are both in horizontal plane.

But what about part b now, the total initial energy =\= energy flowing out of one pipe!!
Pls respond
Anyone out there,
Original post by Theafricanlegend
Right I forgot to read the question Lul. I understand A of my question, It says they are both in horizontal plane.

But what about part b now, the total initial energy =\= energy flowing out of one pipe!!


You are misunderstanding what Bernoulli's equation is actually saying.
The equation states that

for an incompressible non-viscous fluid, the pressure plus the kinetic energy perunit volume plus the potential energy per unit volume is constant at all points along a streamline.


It is not saying that "the rate of flow of energy" is the same.
Original post by Stonebridge
You are misunderstanding what Bernoulli's equation is actually saying.
The equation states that


It is not saying that "the rate of flow of energy" is the same.

Intredasting, that makes sense, I always thought that it meant energy in =energy out for some reason. Mostly because of continuity equation


might as well start pming you, you're the only who answers lmao,

You're a life saver.
Original post by Theafricanlegend
Intredasting, that makes sense, I always thought that it meant energy in =energy out for some reason. Mostly because of continuity equation


might as well start pming you, you're the only who answers lmao,

You're a life saver.


It might be better to post your questions in the physics section rather than here in the general science/technology section.
Please post questions on the forum, though, and not via PM as it's impossible to answer all the pm questions; and furthermore, more people are available to answer and more get the benefit of the replies.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you